1. Field of the Invention
The present invention relates to a valve mechanism, particularly to a valve mechanism which can be used for a tube-type fluid container. Further, the present invention relates to a tube-type fluid container storing a fluid inside it.
2. Description of the Related Art
A valve mechanism as described in Japanese Patent Laid-open No. 2001-179139 has a spherical valve body and a spring for giving momentum to the valve body toward a valve seat has been used. Manufacturing costs of the valve mechanism using the spherical valve body and the spring, however, tend to be high.
A valve mechanism having a resinous valve seat, and a resinous valve body which moves between a closed position in which the valve body contacts the valve seat and an open position in which the valve body separates from the valve seat is commonly used.
In the resinous valve mechanism, it is preferred that the valve mechanism has a simple configuration which can close a fluid flow reliably. Additionally, it is preferred that the configuration can alter a flow rate of the fluid passing through the valve mechanism discretionally according to a pressure applied to the fluid. As matters stand, however, a valve mechanism satisfying these requirements is not reported.
On the other hand, regarding the above type of tubular container, replacing conventional tubes comprising a metal or an aluminum-foil-laminated material, tubes comprising a synthetic resin alone or a lamination of a synthetic resin and aluminum (In this specification, these are named generically as “synthetic-resin-made”.) have been used.
In the case of a tube-type container using a synthetic-resin-made tube, because these synthetic-resin-made tubes have an elasticity recovering force, the following problem occurs: When a pressure is removed after a fluid is discharged by applying the pressure to the tube, the air flows back from an opening portion for discharging the fluid to the fluid storing portion by the elasticity recovering force of the tube, deteriorating the quality of the fluid stored in the fluid storing portion.
For this reason, a tube-type container, in which a tabular valve body is provided in an opening portion for discharging the fluid and the opening portion is closed by this valve body when the original shape of the tube is restored by its elasticity, has been proposed (e.g. in Japanese Patent Laid-open No. 1995-112749, Japanese Patent Laid-open No.1998-157751, Japanese Utility Model Laid-open No.1984-26748, etc.).
In a conventional tube-type container in which the above-mentioned tabular valve body is provided, if the tube recovers its original shape by its elasticity slowly, the valve body fails to close the opening portion of the tube-type container and the air may flow back to the fluid storing portion.
Additionally, the conventional tube-type container in which the above-mentioned tabular valve body is provided has a problem that its durability is low.
Regarding the tube-type container described in Japanese Patent Laid-open No. 1998-157751, as the content is discharged, a shape of the container is changed gradually. Consequently, as the content remaining in the tube-type container is reduced, a shape change of the container increases and it becomes harder to discharge the content from the tube-type container.
For this reason, as described in Japanese Patent Laid-open No. 2000-109103 incorporated, a pneumatically pushed-out tube-type container, which has a double construction dividing the inside of the container into a content chamber and an air chamber is proposed. In this container construction, the content chamber communicates with the outside at its discharge port of the container and the air chamber has a valve construction portion at its bottom, which shuts off the air chamber to prevent the air inside the air chamber from flowing outward when a pressure is applied to the container by pressing down the body portion of the container. Through the valve construction portion, the air chamber communicates with the outside.
The tube-type container described in Japanese Patent Laid-open No. 2000-109103, however, can be used only with high-viscosity contents, because it does not possess a valve mechanism at its discharge port. If a low-viscosity fluid is stored in this tube-type container, there is a problem that the air flows back into the container from the discharge port of the container, lowering the quality of the fluid stored in the container.
Additionally, for the tube-type container described in Japanese Patent Laid-open No. 2000-109103, a valve mechanism needs to be provided in the air chamber. The valve mechanism, however, is generally expensive and increases the manufacturing costs of the tube-type container which should be manufactured inexpensively because it is disposable under normal conditions.
Furthermore, the tube-type container described in Japanese Patent Laid-open No. 2000-109103 has a construction including an air chamber at its body portion of the tube-type container, and a valve construction portion needs to be provided in the body portion. It is difficult, however, to manufacture a tube-type container with a valve construction portion provided at its body portion. Additionally, there is a problem that welding cannot be done satisfactorily due to the valve construction portion when attempting welding the bottom portion of the tube-type container.
The present invention is achieved to solve the above-mentioned problems and aims to provide a tube-type fluid container which prevents the air from flowing back into the container from the discharge port of the container and which can discharge the content easily.